Fluid flow nozzle having temperature compensating means



Aug. 27, 1968 A. B. STOLINS, JR

FLUID FLOW NOZZLE HAVING TEMPERATURE COMPENSATING MEANS Filed May INVENTOR. 427/90 5. fray/v5 Jfi.

M 9 4 mm" United States Patent 3,398,536 FLUID FLOW NOZZLE HAVING TEMPERATURE COMPENSATING MEANS Arthurv B. Stolins, Jr., Costa Mesa, Calif, vassignor to Philco-Ford Corporation, a corporation of Delaware Filed May 25, 1965, Ser. No. 458,694 18 Claims. (Cl. 60-253) contemplated by the invention may be used for a variety of purposes, for example, as prime rnovers for mechanical and electrical devices, and for guidance control, or propulsion, of missiles and space vehicles.

"Ihe burning rates of one known group of solid fuels, such as the fuels frequently used as rocket propellants, depend upon their initial temperatures at the time of firing. Some of these propellants at low initial temperatures will burn slowly and, conversely, at high initial temperatures they will burn rapidly. Other propellants of this group are known to exhibit characteristics directly opposite to those just described. That is, at a low initial temperature a high burning rate results, and at a high initial temperature the result is a loyv burning rate.

The burning rate of these, fuels, in addition to being a function of initial temperature, is also known to be a function of the pressure existing within the combustion chamber. Attempts have been made to' control the pressure within the combustion chamber, and hence 'the burning rate, by controllinglthe area of the discha-rgeo-rifice or nozzle. In order to insure substantially uniform burning rates it is desiable to compensate forrelatively slow burning rates by decreasing the nozzle areaandto compensate for relatively rapid burningjrates by increasing the nozzle area. v

It is an objective of the present invention toprovide an improved orifice or nozzle construction, that is self adjusting to provide controlled throttlin-glof the flowjof gas from the combustionchamber and thereby to compensate for temperature-induced changes in the burning rate of the fuel.

It is a further object of the invention to provide improved .compensating means operable in response to erator orifice area for the duration of gas generation,

It is a feature of the invention that frictional forces, fluid pressure, and temperature conditions co-act ,in novel combination to maintain the cross-section of the nozzle at the value-required for optimum performance under the temperature condition prevailing in the fuel at the time of firing. I

To achieve the objectives of the invention, there is provided, in a preferred embodiment, a two-part gas discharge orifice or nozzle in a generator or motor of the type powered by solid fuel. One nozzle part is rotatable with respect to the other tovary the cross-sectional area of the nozzle and hence to throttle the flow of gas from the combustion chamber with resultant control of the burning rate of the fuel. Bimetallic means interconnects one part of the nozzle with the other part thereof and is operable to rotate one part in response to temperature changes taking place prior to firing. In order that the cross-sectional area of the nozzle which exists- 1 just prior to firing, and which is a function of the tem- 2 perature of the fuel at that time, may be maintained after ignition, the bimetallic means is prevented from rotating said one nozzle part by virtue of a novel arrangement in which the pressure of the discharging gas is used to urge said nozzle parts into frictional engagement with one another, thus tending to prevent relative rotation after ignition. A fusible link is interposed between the bimetallic means and. the movable nozzle part and this link melts shortly after ignition, thus disconnecting the bimetallic element from the nozzle and preventing further undesired adjustment of the nozzle which might result from the high combustion temperature. The invention is additionally characterized by provision of a plenum, chamber defined by the confrontingfr'icticnally engaged surfaces of the nozzle parts, and this chamber is subjected to the reduced static pressure of the rapidly flowing gas, further enhance the desired frictional en gagement of the nozzle parts. Finally, the confronting surfaces of the nozzle parts are so engaged that any differential thermal expansion of the parts creates additional frictional force holding said parts against relative rota- I tion. By co-action of these several instrumentalities the i objectives of the invention may best be achieved will be appreciated upon reference to the following description, taken in light of the accompanying drawing in which:

FIGURE 1 is a sectional view of gas generator apparatus embodying the invention;

FIGURE 2 is a sectional view, with parts removed or broken away, of apparatus illustrated in FIGURE 1 and looking in the direction of arrows 22 applied to the latter; I FIGURE 3 is an exploded view, in perspective, of portions of the apparatus illustrated in FIGURE 2; and

FIGURES 4 and 4A are operational views of apparatus illustrated in FIGURE 2 and looking in the direction of arrows 44 applied thereto.

With more particular reference to the drawing, and first to FIGURES 1 and 2, the invention is illustrated as being embodied in a gas generator housing 10 comprising a combustion chamber 11 having disposed therein a solid fuel charge or grain 12. A nozzle 13, of the convergent-divergent narrow throat type, extends through the wall 14 comprising one end of housing 10. As is best seen in FIGURE 2, the nozzle is, in effect, a venturi tube the longitudinal axis of which is slightly eccentric with respect to the central axis of the cylindrical major body portion of the nozzle, for reasons which will be hereinafter more fully explained.

With reference also FIGURE 3, nozzle 13 is made up of two parts, one part 15 comprising the convergent portion of the nozzle, and slidably abutting the other part 16 comprising the divergent portion. Part 15 has the configuration of a disk provided with an eccentricallly disposed, axially, extending convergent bore, and is mounted for rotation, by means to be described, about the aforesaid central axis with respect to the other part 16.

Rotatable part 15 is arranged to turn within the predetermined fixed limits illustrated in FIGURES 4 and 4A, about an axis which is displaced laterally with respect to the longitudinal axis of the venturi tube. Accordingly, and still with reference to FIGURES 4 and 4A, rotation of movable part 15 moves the convergent nozzle portion transversely with respect to the divergent portion, whereby to vary the elfective throat area of the venturi tube. The limits of rotation of part 15 with respect to part 16 are provided by stud 17 extending axially from an apertured end wall 18 of cylindrical member 19 (see also 3 FIGURE 3) and disposed for releasable abutting engagement with end portions of an arcuate notch 20 formed in a peripheral region of part 15. 1 With further reference to FIGURE 3, movable part 15 of nOZZle 13 is provided with a radially extending pin 21 having an arcuate base portion bonded by solder 22. to part 15. According to the invention, there is utilized a solder having a melting temperature that is substantially the temperature to which the nozzle part 15 will be heated a very short time after ignition of the fuel grain. By this construction, soldered pin 21 comprises a fusible link, in achievement of a mode of operation hereinafter to be more fully described. Pin 21 extends into a laterally opened slot 23 provided in the free end portion of bimetal coil 24 that is coaxial with and spaced from portion 16 of the nozzle. Bimetal coil 24 is affixed at its other end to a stud 25 projecting from flange 26. In the above described arrangement, rotational forces alone will be transmitted to movable part 15 by the free end of thermally activated bimetal coil, through interengagement of pin 21 with slot 23 at the free end of the coil. In the present preferred embodiment, and by way of example, the angular disposition of the free end of the bimetal coil 24 is made to vary at the rate of about 1 degree of rotation per 3 F. change in temperature, the direction of rotation being a function of the temperature-burn rate characteristic of the particular fuel used.

' In provision of rotation of part 15, a longitudinally presented circular rim 27 extends along a peripheral portion of fixed part 16 adjacent part 15. A similarly shaped, lesser diameter peripheral rim 28 of part 15 extends coaxially with rim 27 and is overlapped by that latter as seen in FIGURE 2. In addition to being telescopingly received within outer rim 27, the inner rim 28 extends into abutting, sliding engagement with the smooth, transversely extending face 29 of part 16. Rims 27 and 28, and face 29 are accurately machined for close fit, to provide for substantially frictionless rotation of part 15 relative to part 16 prior to firing. Another rim 30, also accurately machined, is provided on part 15 and extends along the periphery of the narrow throat of the venturi tube. Rim 30, however, does not completely encircle the tube throat, as seen in FIGURE 3. Rim 30 also abuttingly engages the generally planar face 29 of part 16, as shown in FIGURE 2, and cooperates therewith and with similarly abutting rim 28 to form a plenum chamber. This plenum chamber is in fluid flow communication with the venturi tube throat section through the agency of the gap in discontinuous rim 30, and will, therefore, be subject to the relatively low static pressure of the gas flowing at high velocity through the throat section, for reasons that will be hereinafter more fully explained.

With reference to FIGURES 1 and 2, flange 26 of the nozzle part 16 further abuts the edge of the opening in wall 14 through which the nozzle extends, and serves as a thrust plate for the nozzle. Cylindrical member 19 is mated to the flange as shown, and is provided with a dome shaped screen 31 having a flange 32 providing for its screw attachment to flanged extension 33 of end wall 18. End wall 18 and flange 22 have respective axially aligned openings 34 and 35 disposed in registry with the mouth of nozzle part 15. Screen 31 will serve to prevent large particles of the fuel grain from flowing through openings 34 and 35 to enter the nozzle, should such particles become dislodged during firing.

As is illustrated in FIGURE 2, a disk 36 of frangible, liquid impervious membranous material, such, for example, as the material sold under the trade mark Mylar, is clamped between the respective flanges 33 and 32 of member 19 and screen 31 to extend over openings 34 and 35, and serves as a weather seal for the fuel grain prior to firing. Upon firing, this seal is ruptured and blown out by the initial gas flow.

In particular accordance with the invention, cylindrical member 19 encloses bimetal coil 24 and is embedded in the fuel grain 12. By such an arrangement, and as will be more fully appreciated from what follows, bimetal coil 24 will be subjected to the temperature of the grain prior to, and immediately upon ignition of the grain. Accordingly, thermal expansion and contraction of coil 24 will take placerotatably to adjust the position of nozzle part 15 in establishment of the proper throat area at the time of firing. In the present embodiment, and by way of example, there is illustrated in FIGURE 4 the throat opening corresponding to an initial grain temperature of F., and in FIGURE 4A there is illustrated the throat opening corresponding to an initial grain temperature of -65 F., the direction of rotation being a function of the temperature-burn rate of the fuel grain utilized in the preferred embodiment. Just after ignition, bimetal coil 24 will become heated to substantially the temperature of the burning grain.

In order that nozzle 13 maintain the established crosssectional area after the propellant is ignited, in achievement of the desired burning rate, the heated bimetal coil 24 is prevented from rotating the movable part 15 by virtue of rims 28 and 30 of part 15 being urged by the relatively high pressure gas within chamber 11 into high frictional engagement with the face 29 of other part 16. Ignition of the fuel grain is followed substantially instantaneously by melting of solder 22", due to heating by the burning grain, permanently to disconnect the bimetal coil 24 from the movable nozzle part 15, and ensure against possible overriding of the frictional locking forces by the thermally activated coil. Also, as the part 15 is heated its rim 28 expands differentially with respect to rim 27 provided on fixed part 16. Due to the relatively closely machined fit between rims 27 and 28, they will bind frictionally against one another further to lock part 15 to part 16. Further heating of the part 15 causes solder 22 holding the pin 21 to melt, thereby precluding rotation of part 15 by the bimetal coil 24 as it, too, becomes heated further. By virtue of the above described cooperative relationship between elements of the nozzle, the initial positions of part 15, and hence the desired throat area, is maintained throughout burning of the grain.

It will be appreciated that the flow control nozzle of the present invention is susceptible of a number of modifications without departing from the scope of the appended claims. For example, the bimetal coil 24 may be made to have thermal expansion and contraction characteristics in accordance with the burning rate of the particular solid fuel that is used, taking into account that at a predetermined higher temperature some fuels burn at their high rates whereas other fuels burn at their lower rates, and vice versa. As stated above, the nozzle is usable in motor means serving as a prime mover, as well as having utility in auxiliary motor means such as are used for guidance purposes.

I claim:

1. An adjustable gas discharge device for use in the burning of fuel within a combustion chamber, including a nozzle adapted for gas flow communication'with such combustion chamber, said nozzle comprising: an outwardly divergent tubular section; a convergent tubular section associated with said first recited tubular section and in cooperative, substantially axial alignment therewith to define a venturi tube extending along a first axis; and means providing for rotation of one of said tubular sections relative to the other of said tubular sections about a second axis disposed eccentrically with respect to said first recited axis, in response to temperature changes of said nozzle, whereby to vary the effective throat area of said venturi tube.

2. A device according to claim 1, and further characterized in that said last recited means comprises a bimetallic element disposed and adapted to be subject to temperatures prevailing Within such combustion chamber prior to firing of said fuel.

3. A device according to claim 1, and further characterized in that said convergent and said divergent tubular sections include means defining a. plenum chamber in the region of adjacency of said sections and ported to the throat section of said venturi tube, whereby said plenum chamber will be subject to the relatively low static pressure of high velocity gas as it flows through said nozzle to create a reduced pressure between said sections tending to urge the rotatable section into frictional holding engagement with the fixed section for the duration of combustion.

, 4. A device according to claim 1, and characterized in that said convergent tubular section is rotatable with respect to said divergent tubular section.

5. A device according to claim 2, and characterized in that said bimetallic element comprises a thermally activated coil disposed about said tubular sections and connected permanently at its One end to one of said sections, and thermally fusible linkage means connecting the other end of said coil to the other of said sections, said linkage means being operable to disconnect said coil from said other section in response to elevation of the temperature of said nozzle by relatively hot gases flowing therethrough.

6. For use with a gas generating device including a combustion chamber having therein a solid fuel charge adapted to burn at a rate dependent upon the temperature of the charge at the time of its ignition, temperature compensating nozzle means, comprising: axially aligned convergent and divergent nozzle sections cooperably disposed to form a venturi tube in gas flow communication with said chamber; bearing means providing for rotation of said convergent section about an axis displaced laterally with respect to the axis of said venturi tube thereby to vary the effective throat area; and thermally activated means operably coupled with said convergent section to rotate the latter in response to temperature changes in the fuel charge, whereby to establish a predetermined throat area effective to compensate for the different burning rates of the fuel charge.

7. Nozzle means according to claim 6 and characterized further by the inclusion of fusible linkage means operable upon ignition of said charge to decouple said thermally activated means from said convergent section in establishment of said predetermined throat area.

8. Nozzle means according to claim 6, and further characterized in that said bearing means is so constructed and arranged as to lock said convergent nozzle section against further rotation upon ignition of said charge.

9. Nozzle means according to claim 7, and further characterized in that said bearing means is so constructed and arranged as to lock said convergent nozzle section against further rotation upon ignition of said charge.

10. A gas generator of the type having a housing provided with a combustion chamber, means defining a venturi nozzle in gas flow communication with the combustion chamber and including means for varying the size of said throat passage comprising: a pair of generally cylindrical elements in axial alignment, one of which elements is rotatable relative to the other about a common axis, each of said members provided with funnel-shaped apertures defining said venturi nozzle in such a manner that the nozzle axis is displaced laterally with respect to the axis of the cylindrical elements, whereby rotation of one element relative to the other reduces the said passage area, plenum chamber means defined by :adjacently disposed portions of said cylindrical members, and means for porting said plenum chamber means to said throat passage whereby said plenum chamber means will be subject to the relatively low static pressure of high velocity gas flowing through said nozzle, and said members will be urged frictionally together by a resultant vacuum in said plenum chamber means to prevent further relative rotation between said members.

11. In a gas generator, a housing provided with a combustion chamber, a fuel charge disposed within said chamber for producing hot exhaust gases, adjustable nozzle means in gas flow communication with said housing, said nozzle means comprising: a first cylindrical member having a funnel shaped bore arranged on an axis parallel to and spaced laterally from the longitudinal axis of said first member; a second cylindrical member axially aligned with and disposed adjacent the first member, and having a funnel shaped bore nonmally axially aligned with the first recitedbore and cooperably disposed with respect thereto to form a venturi nozzle; an annular recess in the end of one of said members disposed about the relatively narrow region of said venturi nozzle, the adjacent end of the other of said members overlying said annular recess and cooperably disposed therewith to form a substantially sealed plenum chamber; means defining a port providing gas flow communication between said plenum chamber and the throat region of the venturi nozzle; means providing for rotation of one of said members relative to the other, whereby said funnel shaped bores are moved out of axial alignment and the area of the throat region is reduced; and a thermally activated linkage responsive to temperature changes in said fuel charge prior to firing, and operable to rotate the said one member in establishment of a predetermined throat area corresponding to the temperature of said charge at the time of firing, the hot exhaust gases generated upon firing being effective frictionally to urge the said one cylindrical member against the other and to create a vacuum in said plenum chamber due to high velocity gas flow through the nozzle throat area, whereby to provide a holding force preventing said linkage means from further rotating said one cylindrical member.

12. A generator according to claim 11 and further characterized in that said linkage means is decoupled from the said one member in response to the temperature rise of the burning fuel charge.

13. For use in a solid fuel gas generator of the type including a housing provided with a combustion chamber, a nozzle adapted for gas flow communication with said combustion chamber, said nozzle comprising: means defining an outwardly divergent tubular section; means defining a convergent tubular section associated with said first recited tubular section and in cooperative, substantial axial alignment therewith to define a venturi tube extending along a first axis; means providing for rotation of one of said tubular sections relative to the other of said tubular sections about a second axis disposed eccentrically with respect to first recited axis, in response to temperature changes of said nozzle prior to ignition of said solid fuel, whereby to vary the effective throat area of said venturi tube prior to such ignition; and means for preventing rotation of said one section upon ignition of said fuel, including means operable in response to the increase in nozzle temperature resulting from firing to render inoperable said means providing for rotation.

14. An adjustable gas discharge device for use in the burning of fuel within a combustion chamber, including a nozzle adapted for gas flow communication with said combustion chamber, said nozzle comprising: a first tubular section; a second tubular section associated with said first recited tubular section and in cooperative, substantially axial alignment therewith to define anozzle bore extending along a first axis; and means providing for rotation of one of said tubular sections relative to the other of said tubular sections about a second axis disposed eccentrically with respect to said first recited axis, in response to temperature changes of said nozzle, whereby to vary the effective area of said nozzle bore.

15. A device according to claim 14 and further characterize-d in that said last recited means comprises a bimetallic element disposed and adapted to be subject to temperatures prevailing within such combustion chamber prior to firing of said fuel.

16. For use with a gas generating device including a combustion chamber having therein a solid fuel charge adapted to burn at a rate dependent upon the temperature of the charge at the time of its ignition, temperature compensating. nozzle means comprising: axially aligned first and second nozzle sections in gas flow communication with said chamber; bearing means providing for rotation of said first sectionv about an axis displaced laterally with respect to the axis of said nozzle, thereby to vary the effective cross-sectional area of said nozzle; and thermally activated means operably coupled with said first section to rotate the latter in responseto temperature changes in the fuel charge, whereby to establish a predetermined crosssectional area effective to compensate for the different burning rates of the fuel charge.

17. Nozzle means according to claim 16, and characterized further by the inclusion of fusible linkage means operable upon ignition of said charge to decouple said ther- 8 mally activated means from said first section in the establishment of said predetermined cross-sectional area.

18. Nozzle means according to claim 17 and further characterized in that said bearing means is operable to lock said first nozzle section against further rotation upon ignitiOn of said charge.

References Cited UNITED STATES PATENTS 2,612,747 10/1952 Skinner 60-242 X 2,894,692 7/1959 Ledbetter, et a1. 60-242 X 2,909,032 10/1959 Davies 60253 FOREIGN PATENTS 114,144 l/l945 Australia.

CARLTON R. CROYLE, Primary Examiner. 

6. FOR USE WITH A GAS GENERATING DEVICE INCLUDING A COMBUSTION CHAMBER HAVING THEREIN A SOLID FUEL CHARGE ADAPTED TO BURN AT A RATE DEPENDENT UPON THE TEMPERATURE OF THE CHARGE AT THE TIME OF ITS IGNITION, TEMEPERATURE COMPENSATING NOZZLE MEANS, COMPRISING: AXIALLY ALIGNED CONVERGENT AND DIVERGENT NOZZLE SECTIONS COOPERABLY DISPOSED TO FORM A VENTURI TUBE IN GAS FLOW COMMUNICATION WITH SAID CHAMBER; BEARING MEANS PROVIDING FOR ROTATION OF SAID CONVERGENT SECTION ABOUT AN AXIS DISPLACED LATERALLY WITH RESPECT TO THE AXIS OF SAID VENTURI TUBE THEREBY TO VARY THE EFFECTIVE THROAT AREA; AND THERMALLY ACTIVATED MEANS OPERABLY COUPLED WITH SAID CONVERGENT SECTION TO ROTATE THE LATTER IN RESPONSE TO TEMPERATURE CHANGES IN THE FUEL CHARGE, WHEREBY TO ESTABLISH A PREDETERMINED THROAT AREA EFFECTIVE TO COMPENSATE FOR THE DIFFERENT BURNING RATES OF THE FUEL CHARGE. 